Such sensors are suitable for example for measuring the direction of a magnetic field in a plane. Nowadays, sensors are almost exclusively used that measure the components of the magnetic field in relation to two orthogonal coordinate axes. These sensors contain magnetic field sensors such as magnetoresistive components (e.g. Philips KMZ41) or Hall elements (e.g. Sentron 2SA-10). The magnetic field sensors provide two analogue output voltages that are proportional to the sine or cosine function of the direction of the magnetic field. The direction of the magnetic field can be determined from these two output voltages. To do so, on the one hand the quadrant of the field direction has to be determined from the sign of the two output voltages and, on the other hand the arc tangent of the quotients of both output voltages has to be calculated. As an accurate analogue quotient formation is very complex to implement, the quotient formation is often done in a digital way for example by means of the iterative CORDIC algorithm. The digital quotient formation is time-consuming and therefore slow. Furthermore, to carry out these calculations, the sensor must have a microcontroller. Such a sensor is therefore large, expensive and slow.
A sensor of this type is used for example in an angle transmitter in order to measure the direction of a magnetic field produced by a permanent magnet. Here, a further problem exists in that the strength of the magnetic field produced by the permanent magnet is greatly dependent on the temperature of the permanent magnet. This necessitates a large measuring range of the sensor. For sensors that have a ferromagnetic core for the passive amplification of the magnetic field, the danger exists that the magnetic field saturates the ferromagnetic core or at least partially saturates it, which leads to measurement errors.
A sensor suitable for determining the direction of a two-dimensional magnetic field is Known from EP 1182461. The sensor comprises a magnetic field concentrator with a flat shape and two magnetic field sensors that comprise at least one Hall element whereby the Hall elements are arranged in the area of the edge of the magnetic field concentrator. The first magnetic field sensor measures a first component of the magnetic field and the second magnetic field sensor measures a second component of the magnetic field. The direction of the magnetic field can therefore be determined from the signals of the two magnetic field sensors.
The object of the invention is to develop a sensor with which the direction of the external magnetic field in a plane can be determined in a simple manner.